I run a home daycare and I have done lots of potty training. I just trained my 3 yr. old nephew who is in care here. What I did for him was this. Really funny, because he didn't want to get rid of diapers either. Follow what the other mom said and go together to get undies, his favorite kind and buy some stickers.
Sticker chart, if you don't have one, I can email you what we use, blank to say anything you want or one that says I went Potty this many time today. Really Neat. Anyhoo...I gave him a goal, his first week was a trip to the Snow Cone stand and if he filled up that chart that week he could. If he goes when I take him = 1 sticker and if he goes without being asked or taken/tells me he has to go then he gets 2 stickers. It doesn't take long to fill up the chart at all. Anhoo....
Just some suggestions. Change up the goals. Not too big, but if he feels like he working toward something then it makes him more eager to go...I had my 3 yr. old nephew trained in 3 weeks. Week # 2 he started wearing underwear all the time and didn't have one accident. By week 3 he was out of diapers all together and doing great even at night. So, if you want to try that. Put all the suggestions together and see how that works.
Good Luck, T.!